Ranitidine hydrochloride, as described and claimed in British Patent Specification No. 1,565,966, (Apr. 1980) and U.S. Pat. No. 4,128,658 (Dec. 1978) shows potent histamine H.sub.2 -blocking activity.
A process for preparing ranitidine hydrochloride is known and described in U.S. Pat. No. 4,128,658 (Dec. 1978) and British Patent Specification No. 1,565,966 (Apr. 1980). In U.S. Pat. No. 4,521,431 (June 1985), the ranitidine hydrochloride produced by the method described in U.S. Pat. No. 4,128,658 (Dec. 1978) and British Patent Specification No. 1,565,966 (Apr. 1980) was designated as crystalline Form 1 of ranitidine hydrochloride. A process for preparing crystalline Form 2 ranitidine hydrochloride was disclosed in U.S. Pat. No. 4,521,431 (June 1985), which is now commercially produced and marketed by Glaxo Holdings, the owner of the foregoing patents.
According to Glaxo, the described method to produce Form 1 ranitidine hydrochloride in U.S. Pat. No. 4,128,658 (Dec. 1978), does not have the desirable features of a manufacturing process and the product has unsuitable filtration and drying characteristics. During recent legal proceedings, Glaxo has also stated that it is not possible to manufacture crystalline Form 1 ranitidine hydrochloride on a commercial scale and moreover, that Form 1 is unstable and gets converted into stable Form 2 quickly. All attempts made so far by many researchers around the world to produce Form 1 ranitidine hydrochloride as per the described method in U.S. Pat. No. 4,128,658 (Dec. 1978) in the laboratory have failed.